Avoiding a void with grout

Applying grout to steel columns and the like sounds simple in theory, but in practise it is quite a specialist process. As with most things in life, lack of proper preparation will lead to poor results.

Filling the gap that exists between a steel plate and substrate when used to secure columns and machinery requires a grout that is easily poured and flows evenly around the void. This is best achieved by installing wooden formwork around the base plate and pouring into a header box/hopper for continuous flow to ensure an even application and prevent any air entrapment.

With cementitious grout, its long-term success is largely decided at the mixing stage – too much water will affect its overall strength; too little will affect its flowable capabilities. As an alternative void-filler for base plates and such, it's not uncommon for builders to use hand-applied repair mortar. But this is far from ideal as an even application is almost impossible to achieve, thus air bubbles and gaps are a likely result.

Sink the shrink

Any product containing cement will ultimately shrink and create gaps; therefore a shrinkage compensated grout is essential. If applying a grout to a concrete substrate it's essential to pre-soak the substrate in clean water for a minimum of two hours beforehand. Failure to do so is likely to result in the concrete extracting from the grout, affecting its cure, leaving a potential for cracking and reduced adhesion.

The SikaGrout^® range contains high-quality, flowable, cementitious grouts for general purpose or large commercial applications. SikaGrout^®111GP, for instance, meets the requirements of Class R4 of BS EN 1504-6. Pumped or poured, it's ideal for a number of solutions including machine and base plate-filling, concrete repairs and steel reinforcement anchoring. Specifying the correct quantity and strength of grout is a basic requirement for a quality application, but it's a simple trick that can sometimes be missed.

Expert advice

Specifying the correct quantity and strength of grout is a basic requirement for a quality application, but it's a simple trick that can sometimes be missed. Sika's technical team is available to eliminate the risk of such oversights. Our staff have the necessary expertise and product information to ensure correct grout quantity and type for a particular project and are also available for site visits to offer application guidance.

Cementitious grout – once it's fully cured – can achieve compressive strengths greater than standard C40 concrete. Attempting to remove it from beneath a steel base plate due to specification or application error could result in a very long and costly process. Better, then, to ensure this simple but extremely important task is carried out correctly – which means paying close attention to the product data sheet before the grout-pouring begins. In these instances, there is no such thing as being over-prepared.

By Steven Hardy, Sika Technical Services Advisor – Refurbishment

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